Methods and system for automatic user-configurable steering parameter control

ABSTRACT

A vehicle guidance system and method for automatically adjusting an amount of a user-configurable steering parameter applied to at least one steerable wheel of a vehicle. The vehicle guidance system may comprise a computing device for receiving a desired angle of the steerable wheel, measuring the actual angle of the steerable wheel, and comparing the actual angle with the desired angle. The computing device may then decrease the user-configurable steering parameter automatically if over-steering has occurred, meaning the actual angle of the wheel is determined to be greater than the desired angle of the wheel and angled in the same direction as the desired angle, or the computing device may increase the user-configurable steering parameter automatically if under-steering has occurred, meaning the actual angle of the wheel is determined to be less than the desired angle of the wheel or is angled in the opposite direction as the desired angle.

BACKGROUND

1. Field

Embodiments of the present invention relate to methods and systems forautomatically adjusting a user-configurable steering parameter ofvehicle guidance systems. More particularly, the invention relates tomethods and systems for determining if under-steering or over-steeringis occurring during operation of a vehicle and automatically adjustingthe user-configurable steering parameter accordingly.

2. Related Art

Vehicle guidance systems use control algorithms to direct vehicles fromlocation to location. Each vehicle's architecture, such as front wheelsteering, rear wheel steering, etc., can affect the steering performanceof the vehicle. Furthermore, ground conditions or the addition of animplement, such as a trailer hitched to a vehicle, may also contributeto a vehicle's steering performance. These and other variable factorscan affect the guidance system's ability to get the vehicle to thedesired path (i.e. the path defined by the guidance system) in a timely,comfortable, and optimal manner.

Some guidance systems allow an operator to vary different parameters ofthe control algorithms to maintain equivalent steering performanceindependent of the vehicle architecture. Specifically, operators of somevehicle guidance systems may adjust a user-configurable steeringparameter such as steering gain or sensitivity to accommodate forvarying vehicle architectures, attachments, and ground conditions.However, if the parameters for the control algorithms or theuser-configurable steering parameters are not set correctly, optimalsteering performance may not be achieved. Additionally, if ground orvehicle conditions change during operation, such as moving from soil toclay or having liquid tanks empty throughout a field, the vehicle mayalso move further away from optimal performance.

Selecting a user-configurable steering parameter value that is too highcan make the steering system too aggressive and causes what is referredto as over-steering. Selecting a user-configurable steering parametervalue that is too low can make the steering system response too sluggishand causes what is referred to as under-steering. Though the operatormay have access to adjust the user-configurable steering parameter, suchas the steering gain, during operation of the vehicle, there is a pointat which the operator can't distinguish the change in performance, eventhough there is some degradation.

Accordingly there is a need for a method for dynamically and accuratelyadjusting the steering gain of a vehicle guidance system duringoperation the does not suffer from the problems and limitations of theprior art.

SUMMARY

Various embodiments of the invention provide a vehicle guidance systemand method for automatically adjusting an amount of a user-configurablesteering parameter, such as steering gain or sensitivity, applied to atleast one steerable wheel of a vehicle in order to optimize the steeringperformance of the vehicle. The vehicle guidance system may comprise alocation determining component, a computing device, memory, and an anglemeasurement device.

The location determining component may be a GPS receiver that determinesposition data based on received satellite signals. The computing devicemay have algorithms which use inputs from a user and/or the locationdetermining component to form command signals for the desired rotationalspeed and desired turn angle of the wheels of the vehicle. The desiredangle may be sent to a compensation module of the computing device.Additionally, the angle measurement device may measure the actual angleof the wheel for a given point in time and send this value to thecompensation module as well.

The compensation module may compare the actual angle of the wheel withthe desired angle of the wheel to determine if the actual angle is equalto or within an acceptable range of deviation from the desired angle.The compensation module may then decrease the user-configurable steeringparameter automatically if over-steering has occurred, wherein theactual angle of the wheel is greater than the desired angle of the wheeland angled in the same direction as the desired angle. Conversely, thecompensation module may increase the user-configurable steeringparameter automatically if under-steering has occurred, wherein theactual angle of the wheel is less than the desired angle of the wheel oris angled in the opposite direction as the desired angle.

In preferred embodiments of the invention, the computing device mayrecord a history of incidents of under-steering and over-steering, andadjust the user-configurable steering parameter automatically when apre-determined limit of incidents are recorded during a pre-determinedperiod of time. Furthermore, the computing device may calculate theaverage deviation of the actual wheel angles from the desired wheelangles of the recorded incidents over the pre-determined period of timeand adjust the user-configurable steering parameter based on the averagedeviation.

In other various embodiments of the invention, the computing device mayseparately count incidents of over-steering and incidents ofunder-steering, so that the user-configurable steering parameter may beautomatically adjusted when a predetermined limit of over-steeringincidents or under-steering incidents are recorded during apre-determined period of time. Furthermore, the computing device maycalculate the average deviation of the actual wheel angles from thedesired wheel angles of the recorded over-steering or under-steeringincidents over the pre-determined period of time and may adjust theuser-configurable steering parameter based on this average and whetherthe limit for occurrences of over-steering or under-steering has beenreached.

In other various embodiments of the invention, the computing device mayhave a manual mode in which the user may control the user-configurablesteering parameter adjustments manually during operation of the vehicle.

These and other important aspects of the present invention are describedmore fully in the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a schematic plan view of a vehicle having a vehicle guidancesystem and a plurality of wheels according to an embodiment of theinvention;

FIG. 2 is a fragmentary plan view of the vehicle of FIG. 1 and one ofits wheels, wherein the wheel is steerable;

FIG. 3 is a block diagram illustrating certain components of the vehicleguidance system of FIG. 1;

FIG. 4 is a schematic diagram of a Global Positioning System (GPS) thatmay be used to send GPS signals to the vehicle guidance system of FIG.1;

FIG. 5 is a block diagram of the vehicle guidance system of FIG. 1 andits inputs and outputs;

FIG. 6 is a graph of two example sets of data of the actual angles ofsteerable wheels compared with the desired angles of the steerablewheels over a period of time;

FIG. 7 is a graph comparing actual angles to desired angles of thesteerable wheels over a period of time as in FIG. 6, further including arange of acceptable deviation of the actual angle from the desired anglefor each point in time;

FIG. 8 is a flow chart illustrating method steps that may be performedby the vehicle guidance system of FIG. 1; and

FIG. 9 is a flow chart illustrating method steps that may be performedby the vehicle guidance system of FIG. 1.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention references theaccompanying drawing figures that illustrate specific embodiments inwhich the present invention can be practiced. The embodiments areintended to describe aspects of the invention in sufficient detail toenable those skilled in the art to practice the invention.

Other embodiments can be utilized and changes can be made withoutdeparting from the scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense.

Embodiments of the present invention provide a vehicle guidance system10 preferably incorporated as part of a land-based vehicle 12. Asillustrated in FIGS. 1-2, the land-based vehicle 12 may be anagricultural vehicle, automobile, all-terrain vehicle, or any other typeof land-based vehicle known in the art. The vehicle may include aplurality of wheels 14, with at least one steerable wheel 16 operable toturn, pivot, and/or rotate about a center axis 18 such that the vehicle12 may be steered in the direction in which the wheel 16 turns, pivots,or rotates.

The vehicle guidance system 10 can be implemented in hardware, software,firmware, or a combination thereof. An exemplary embodiment of thevehicle guidance system 10 may comprise a location-determining component20, at least one computing device 22, a display 24, memory 26, a userinterface 28, a power source 30, one or more I/O ports 32, and an anglemeasurement device 34, as illustrated in FIG. 3. The guidance system 10is operable to adjust a user-configurable steering parameter, such assteering gain, steering sensitivity, steering force, etc., of thevehicle 12 automatically during operation of the vehicle 12 bycalculating the required user-configurable steering parameter or therequired adjustment of the user-configurable steering parameter based onan actual angle of the steerable wheel 16 at various points in time asmeasured by the angle measurement device 34, illustrated in FIG. 3.

The location-determining component 20, which may be mounted to thevehicle 12, determines positions of the vehicle guidance system 10 as itis moved from place to place and generates and sends correspondingposition data to the computing device 22. In one embodiment, thelocation-determining component 20 may be a satellite navigation receiverthat works with a global navigation satellite system (GNSS) such as theglobal positioning system (GPS) primarily used in the United States, theGLONASS system primarily used in the Soviet Union, or the Galileo systemprimarily used in Europe.

For example, FIG. 4 shows a representative view of a GPS denotedgenerally by reference numeral 36. A plurality of satellites 38 are inorbit about the Earth 40. The orbit of each satellite is not necessarilysynchronous with the orbits of other satellites and, in fact is likelyasynchronous. The location-determining component 20 is shown as a GPSreceiver, receiving spread spectrum GPS satellite signals from thevarious satellites 38.

The spread spectrum signals continuously transmitted from each satellite38 utilize a highly accurate frequency standard accomplished with anextremely accurate atomic clock. Each satellite 38, as part of its datasignal transmission, transmits a data stream indicative of thatparticular satellite. As a GPS receiver, the location-determiningcomponent 20 must acquire spread spectrum GPS satellite signals from atleast three satellites for the location-determining component 20 tocalculate its two-dimensional position by triangulation. Acquisition ofan additional signal, resulting in signals from a total of foursatellites, permits the location-determining component 20 to calculateits three-dimensional position.

The location-determining component 20 may include an antenna to assistin receiving the satellite signals. The antenna may be a any type ofantenna that can be used with navigational devices to receive satellitesignals. The location-determining component 20 is operable to receivenavigational signals from the GPS satellites 38 and to calculatepositions of the location-determining component 20 as a function of thesignals. The location determining component 20 may send these calculatedpositions to the computing device 22 to determine track logs or anyother series of geographic coordinates corresponding to points along apath traveled by the vehicle 12. The computing device 22 is alsooperable to calculate routes to desired positions, provide instructionsto navigate to the desired positions, display maps and other informationon the display screen 24, and execute other functions as describedherein.

Although one embodiment of the vehicle guidance system 10 describes thelocation-determining component 20 as a GPS receiver, it is noted thatequivalents may be employed and substitutions made without departingfrom the scope of the invention as recited in the claims. For example,in other embodiments of the invention, the location determiningcomponent 20 need not directly determine its current geographicposition. For instance, the location determining component 20 maydetermine the current geographic position by receiving positioninformation directly from the user, through a communications network, orfrom another electronic device.

The location determining component 20 may include one or moreprocessors, controllers, or other computing devices and memory so thatit may calculate position and other geographic information without thecomputing device 22. Further, the location determining component 20 maybe integral with the computing device 22 such that the locationdetermining component 20 may be operable to specifically perform thevarious functions described herein. Thus, the computing device 20 andlocation determining component 20 can be combined or be separate orotherwise discrete elements.

The display 24 is coupled with the computing device 16 and is operableto display various information corresponding to the vehicle 12 and itsguidance system 10, such as maps, positions, and directions as describedbelow. The display 24 may comprise conventional black and white,monochrome, or color display elements including CRT, TFT, LCD, and/orplasma display devices. Preferably, the display 24 is of sufficient sizeto enable a user to easily view it while driving the vehicle 12.

The display 24 may be integrated with the user interface 28, such as inembodiments where the display 24 is a touch-screen display to enable theuser to interact with it by touching or pointing at display areas toprovide information to the guidance system 10.

The computing device 22 may include any number of processors,controllers, integrated circuits, programmable logic devices, or othercomputing devices and resident or external memory for storing data andother information accessed and/or generated by the vehicle guidancesystem 10. The computing device 22 is preferably coupled with thelocation-determining component 20, the display 24, the memory 26, theuser interface 28, and other components through wired or wirelessconnections, such as a data bus 36, to enable information to beexchanged between the various components.

The computing device 22 may implement a computer program and/or codesegments to perform the functions described herein. The computer programpreferably comprises an ordered listing of executable instructions forimplementing logical functions in the computing device 22. The computerprogram can be embodied in any computer-readable medium for use by or inconnection with an instruction execution system, apparatus, or device,and execute the instructions. In the context of this application, a“computer-readable medium” can be any means that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.The computer-readable medium can be, for example, but not limited to, anelectronic, magnetic, optical, electro-magnetic, infrared, orsemi-conductor system, apparatus, device or propagation medium. Morespecific, although not inclusive, examples of the computer-readablemedium would include the following: an electrical connection having oneor more wires, a portable computer diskette, a random access memory(RAM), a read-only memory (ROM), an erasable, programmable, read-onlymemory (EPROM or Flash memory), an optical fiber, and a portable compactdisk read-only memory (CDROM).

The memory 26, may be integral with the location determining component20, integral with the computing device 22, stand-alone memory, or acombination of both. The memory may include, for example, removable andnon-removable memory elements such as RAM, ROM, flash, magnetic,optical, USB memory devices, and/or other conventional memory elements.

The memory 26 may store various data associated with the operation ofthe guidance system 10, such as the computer program and code segmentsmentioned above, or other data for instructing the computing device 22and system elements to perform the steps described herein. Further, thememory 26 may store various cartographic data corresponding togeographic positions including map data and map elements, such asthoroughfares, terrain, alert positions, points of interest, geographicentities, radio stations, and other navigation data to facilitate thevarious navigation functions provided by the vehicle guidance system 10.Additionally, the memory 26 may store destination addresses andpreviously calculated or otherwise acquire routes to various destinationaddresses for later retrieval by the computing device 22. The variousdata stored within the memory 26 may also be associated within one ormore databases to facilitate retrieval of the information.

The user interface 28 permits a user to operate the vehicle guidancesystem 10 and enables users, third parties, or other devices to shareinformation with the guidance system 10. The user interface 28 maycomprise one or more functionable inputs such as buttons, switches,scroll wheels, a touch screen associated with the display 24, voicerecognition elements such as a microphone, pointing devices such asmice, touchpads, tracking balls, styluses, a camera such as a digital orfilm still or video camera, combinations thereof, etc. Further, the userinterface 28 may comprise wired or wireless data transfer elements suchas a removable memory including the memory 26, data transceivers, etc.,to enable the user and other devices or parties to remotely interfacewith the guidance system 10. The device may also include a speaker forproviding audible instructions and feedback.

The user interface 28 may be operable to provide various information tothe user utilizing the display 24 or other visual or audio elements suchas a speaker. Thus, the user interface 28 enables the user and guidancesystem 10 to exchange information relating to the guidance system 10,including geographic entities, configuration information securityinformation, preferences, route information, points of interests, alertsand alert notification, navigation information, waypoints, a destinationaddress, etc.

The power source 30 provides electrical power to various guidance system10 elements. For example, the power source 30 may be directly orindirectly coupled with the location-determining component 20, thecomputing device 22, the display 24, the memory 26, and the userinterface 28. The power source 30 may comprise conventional power supplyelements such as batteries, battery packs, etc. The power source 30 mayalso comprise power conduits, connectors, and receptacles operable toreceive batteries, battery connectors, or power cables.

The I/O ports 32 permit data and other information to be transferred toand from the computing device 22 and the location-determining component20. The I/O ports 32 may include a TransFlash card slot for receivingremovable TransFlash cards and a USB port for coupling with a USB cableconnected to another computing device such as a personal computer.Navigational software, cartographic maps, and other data and informationmay be loaded in the guidance system 10 via the I/O ports 32.

The angle measurement device may sense the angle of the steerable wheel16 directly through an angle-sensing transducer or may include a camerafor visual inspection of the actual angle of the wheel 16 by thecomputing device 22. However, any means of measuring or sensing angles,as known in the art, may be used.

The components illustrated in FIG. 3 and described herein need not bephysically connected to one another since wireless communication amongthe various depicted components is permissible and intended to fallwithin the scope of the present invention.

In various embodiments of the invention, as illustrated in FIG. 5, thecomputing device 22 may be comprise a control module 42 programmed withcontrol algorithms 44 and operable to receive real-time positioninformation 46 and desired path parameters 48 from any external orinternal source. The control module 42 may process this data in order toproduce a plurality of output commands, such as desired wheel speed anddesired wheel angle for given points in time. The computing device 22may also comprise a compensation module 50 which may receive the desiredwheel angle from the control module 42 and actual angle measurements 52from the angle measurement device 34 to determine the user-configurablesteering parameter required for optimal steering performance. Thecompensation module 50 may also output a steering signal 54 to a wheelactuator (not shown) for physically turning the wheel 16. The steeringsignal 54 may be calculated based on control commands output by thecontrol module 42 and the user-configurable steering parametercalculated by the compensation module 50. The compensation module 50 mayadditionally receive user input 56 from the user interface 28 when thesystem is placed in a “manual” mode. Additionally, the compensationmodule 50 may receive user input 56 to define an acceptable amount ofdeviation between the actual angle of the wheel 16 and the desired angleof the wheel 16.

In operation, the vehicle guidance system 10 may automatically adjustthe user-configurable steering parameter of the vehicle 12. For example,the user-configurable steering parameter may be adjusted to increase ordecrease the force at which the steerable wheel 16 is turned eitherright or left, thereby affecting the steering response, sensitivity, orthe reaction time for the wheel 16 to reach the desired angle ascommanded by the vehicle guidance system 10.

For example, as illustrated in FIG. 6, the vehicle guidance system 10may define a desired wheel angle 58 for a plurality of points in timebased on the dersired steering path 48, thereby determining how far leftand how far right the wheel 16 should turn at given points in time inorder to precisely follow this desired path 48. It should be understoodthat the vehicle 12 may travel in a straight line when the wheel 16 isaligned with the center axis 18. The center axis 18 therefore representsa zero-degree turn of the wheel 16. The actual angles of the wheel 16may be measured in respect to the center axis 18.

FIG. 6 graphs a first set of actual angles 60 and a second set of actualangles 62 to demonstrate under-steering and over-steering. The first setof actual angles 60 demonstrates over-steering, meaning theuser-configurable steering parameter, referred to as gain in thisexample, is set too high. Notice that, at most points in time, theover-steered actual angle 60 exceeds the desired angle 58 in the samedirection from the center axis 18 as the desired angle 58. The secondset of actual angles 62 demonstrates under-steering, meaning theuser-configurable steering parameter, or steering gain in this example,is set too low. Notice that, at most points in time, the under-steeredactual angle 62 is either less than the desired angle 58 or in theopposite direction from the center axis 18 as the desired angle 58.

A small amount of deviation of the vehicle 12 from the desired path 48may be acceptable in various situations. Therefore, as illustrated inFIG. 7, an acceptable range of deviation 64 may be defined either by auser or by the computing device 22. Note that, in FIG. 7, theuser-configurable steering parameter is also denoted as steering “gain”for purposes of this example. The acceptable range of deviation 64 has aleft limit 66 and a right limit 68 and is used to limit how far left ofthe desired angle 58 and how far right of the desired angle 58 theactual angle 60,62 may be at any given point in time. For example, FIG.7 also graphs two sets of actual wheel angles 60,62 over a period oftime compared with the desired angles 58 over the same period of time.At a first point in time 68, both of the actual angles 60,62 are withinthe acceptable range of deviation 64. At a second point in time 70, bothof the actual angles 60,62 are still within the acceptable range ofdeviation 64, even though the steering performance of both, as graphedthus far, is poor. However, at a third point in time 72, both of theactual angles 60,62 should be right of the center axis 18, but bothactual angles 60,62 are outside of the acceptable range of deviation 64.At the third point in time 72, the actual angle 60 is too far to theright, indicating that the vehicle 12 suffers from over-steering.Meanwhile, the actual angle 62 is to the left of the center axis 18,indicating that the vehicle 12 suffers from under-steering. Therefore,in various embodiments of the invention, the compensation module 50determines if the actual angle 60,62 is outside of the acceptable rangeof deviation 64 and then determines if the deviation demonstrates anoccurrence of over-steering or under-steering.

Specifically, as illustrated in FIG. 8, the compensation module 50 mayperform the following steps. First the desired angle and the actualangle may be received by the compensation module 50, as in step 102.Then the compensation module 50 may compare the actual angle of thewheel 16 to the desired angle of the wheel 16, as in step 104. If theactual angle is the same as the desired angle or is within thepre-defined acceptable range of deviation 64 from the desired angle,then the user-configurable steering parameter, denoted as steering gainin this example, is not adjusted, as shown in step 106. However, if theactual angle is not within the acceptable range of deviation 64, thenthe compensation module 50 may determine if under-steering orover-steering has occurred, as shown in step 108. If over-steering hasoccurred, such that the actual angle is greater than the desired angleand in the same direction from the center axis 18 as the desired angle,then the user-configurable steering parameter or steering gain may bedecreased, as shown in step 110. If under-steering has occurred, suchthat the actual angle is less than the desired angle or is in theopposite direction from the center axis 18 of the desired angle, thenthe user-configurable steering parameter or steering gain may beincreased, as shown in step 112.

In a preferred embodiment of the invention, the compensation module mayrecord the actual angle of the steerable wheel 16 for a plurality ofpoints of time over a pre-determined period of time into memory 20. Thecompensation module 50 may also record how many incidents ofunder-steering and over-steering outside of the acceptable range ofdeviation 64 occur in the pre-determined period of time. If apre-determined threshold of incidents is reached or exceeded within thepre-determined period of time, then the compensation module 50 mayautomatically adjust the user-configurable steering parameteraccordingly. If the threshold of incidents is reached or exceeded withinthe pre-determined period of time, the compensation module 50 maycalculate the required user-configurable steering parameter using theaverage amount of deviation of the actual angle from the desired anglefor each recorded incident over the pre-determined period of time.Specifically, the incidents may be organized by whether over-steering orunder-steering occurred, and then the frequency of over-steeringoccurrences may be compared with the frequency of under-steeringoccurrences to determine if the user-configurable steering parameterneeds to be increased or decreased.

For example, if under-steering incidents are recorded four times asfrequently as over-steering during the pre-determined period of time,then the compensation module 50 may calculate the average deviation ofthe actual angle from the desired angle for each occurrence ofunder-steering incidents during the pre-determined period of time. Thisaverage of deviations for under-steering incidents may then be used todetermine by what amount the user-configurable steering parameter shouldbe increased to compensate for the under-steering. Additionally, thethreshold of incidents allowed within a period of time may be specificto over-steering or under-steering, as opposed to an overall incidentcount of both under-steering and over-steering occurrences. So, forexample, if the number of recorded over-steering occurrences exceeds thethreshold of incidents, the user-configurable steering parameter may beadjusted.

One example of the methods described above is illustrated in FIG. 9,inwhich the user-configurable steering parameter is denoted as steeringgain. First the compensation module 50 may retrieve the desired angleand the actual angle for a current point in time, as in step 202. Next,the compensation module 50 may determine if the actual angle is the sameas the desired angle or within the pre-defined acceptable range ofdeviation 64 from the desired angle, as in step 204. If the actual angleis within the pre-defined acceptable range of deviation 64, then step202 may be repeated, with the compensation module 50 retrieving the nextactual angle and desired angle for the next point in time. Otherwise,the compensation module 50 may determine if under-steering or oversteering has occurred, as in step 206.

If under-steering has occurred, then the incident may be added to anunder-steering incident count total and the difference between theactual angle and the desired angle may be recorded in memory 20, as instep 208. Then the compensation module 50 may determine if apre-determined amount of time has passed, as in step 210. If thepre-determined amount of time has not passed, the compensation module 50may return to step 202, obtaining the next angle values. If thepre-determined amount of time has passed, then the compensation module50 may determine if the number of under-steering incidents exceeded theincident threshold during the pre-determined period of time, as in step212. If the threshold was not exceeded, then the compensation module 50may reset the under-steering incident count, as in step 214 and thenrepeat step 202, obtaining the next angle values. If the threshold wasexceeded, the compensation module 50 may average the amounts ofdeviation between the actual angle and the desired angle for theunder-steering incidents within the pre-determined period of time anduse this average to calculate the required user-configurable steeringparameter or steering gain, as in step 216. After step 216, thecompensation module 50 may output the calculated user-configurablesteering parameter or steering gain, as in step 218, reset theunder-steering incident count, as in step 214, and then return to step202, obtaining the next angle values.

If over-steering has occurred, then the incident may be added to anover-steering incident count total and the difference between the actualangle and the desired angle may be recorded in memory, as in step 220.Then the compensation module 50 may determine if a pre-determined amountof time has passed, as in step 222. If the pre-determined amount of timehas not passed, the compensation module 50 may return to step 202,obtaining the next angle values. If the pre-determined amount of timehas passed, then the compensation module 50 may determine if the numberof over-steering incidents exceeded the incident threshold during thepre-determined period of time, as in step 224. If the threshold was notexceeded, then the compensation module 50 may reset the under-steeringincident count, as in step 226 and then repeat step 202, obtaining thenext angle values. If the threshold was exceeded, the compensationmodule 50 may average the amount of deviation between the actual angleand the desired angle for the over-steering incidents within thepre-determined period of time and use this average to calculate therequired user-configurable steering parameter or steering gain, as instep 228. After step 228, the compensation module 50 may output thecalculated user-configurable steering parameter or steering gain, as instep 230, reset the under-steering incident count, as in step 226, andthen return to step 202, obtaining the next angle values.

Although the invention has been described with reference to theembodiments illustrated in the attached drawings, it is noted thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims. Forexample, the methods disclosed herein and illustrated in FIGS. 8-9 maybe performed in any order and steps may be added or deleted withoutdeparting from the scope of the invention as recited in the claims.Also, the user-configurable steering parameter may include parameterssuch as steering gain, steering sensitivity, steering force, etc.Additionally, the user-configurable steering parameter need not beconfigured by a user, but may rather be configured or adjusted by theguidance system, as described above. Finally, the steerable wheel 16 mayalternatively be a belt and track arrangement operable to advance andsteer the vehicle such as used on a tank or various farm implements.

Having thus described an embodiment of the invention, what is claimed asnew and desired to be protected by letters Patent includes thefollowing:

1. A method for adjusting a user-configurable steering parameter of asteerable wheel of a vehicle, the method comprising: measuring an actualangle of the steerable wheel at each of a plurality of points in time;determining if the actual angle of the wheel is outside of an acceptablerange of deviation from a desired angle for each of the plurality ofpoints in time using a data processor; adjusting the user-configurablesteering parameter automatically using the data processor duringoperation of the vehicle if the actual angle of the wheel is outside ofthe acceptable range of deviation; determining if under steering orover-steering has occurred using the data processor; automaticallyadjusting the user-configurable steering parameter down whenover-steering occurs; and automatically adjusting the user-configurablesteering parameter up when under-steering occurs.
 2. The method of claim1, wherein the acceptable range of deviation is the maximum amount tothe left and to the right that the actual angle of the steerable wheelmay deviate from the desired angle of the steerable wheel for aplurality of points in time, and wherein the desired angle is defined bya vehicle guidance system.
 3. The method of claim 1, wherein the vehicletravels in a straight line when the steerable wheel is aligned with acenter axis, the center axis representing a zero-degree turn of thesteerable wheel.
 4. The method of claim 1, wherein the data processordetermines that over-steering has occurred if the actual angle isoutside of the acceptable range of deviation and is greater than thedesired angle in the same direction from a center axis as the desiredangle.
 5. The method of claim 1, wherein the data processor determinesthat under-steering has occurred if the actual angle is outside of theacceptable range of deviation and is less than the desired angle or isin the opposite direction from a center axis as the desired angle. 6.The method of claim 1, further comprising recording a history ofincidents of under-steering and over-steering using the data processor,and adjusting the user-configurable steering parameter automaticallywhen a pre-determined limit of incidents are recorded during apre-determined period of time.
 7. The method of claim 6, furthercomprising calculating the average deviation of the actual wheel anglesfrom the desired wheel angles of the recorded incidents over thepre-determined period of time using the data processor and adjusting theuser-configurable steering parameter based on the average deviation. 8.The method of claim 6, further comprising: separately counting incidentsof over-steering and incidents of under-steering; and automaticallyadjusting the user-configurable steering parameter when a predeterminedlimit of over-steering incidents or under-steering incidents arerecorded during a pre-determined period of time.
 9. The method of claim8, further comprising calculating the average deviation of the actualwheel angles from the desired wheel angles of the recorded over-steeringor under-steering incidents over the pre-determined period of time usingthe data processor and adjusting the user-configurable steeringparameter based on the average and whether the limit for incidents ofover-steering or under-steering has been reached.
 10. The method ofclaim 1, further comprising commanding the processor to switch to amanual mode, wherein the user may control the user-configurable steeringparameter adjustments during operation of the vehicle.
 11. A method foradjusting a user-configurable steering parameter of a steerable wheel ofa vehicle, the method comprising: measuring an actual angle of thesteerable wheel at each of a plurality of points in time; determining ifthe actual angle of the wheel is outside of an acceptable range ofdeviation from a desired angle for each of the plurality of points intime using a data processor; adjusting the user-configurable steeringparameter automatically using the data processor during operation of thevehicle if the actual angle of the wheel is outside of the acceptablerange of deviation; and commanding the processor to switch to a manualmode, wherein the user can control the user-configurable steeringparameter adjustments during operation of the vehicle.
 12. The method ofclaim 11, wherein the acceptable range of deviation is the maximumamount to the left and to the right that the actual angle of thesteerable wheel may deviate from the desired angle of the steerablewheel for a plurality of points in time, and wherein the desired angleis defined by a vehicle guidance system.
 13. The method of claim 11,wherein the vehicle travels in a straight line when the steerable wheelis aligned with a center axis, the center axis representing azero-degree turn of the steerable wheel.